Thermo-electric ammeter.



P. M. LINCOLN.

THERMO ELECTRlC AMMETER. APPL'lcATloN mm ri. i2, x91`3.

1,142,898. Patented June 15, 195'.

wrmissss mvm'rn/ Panni. Lmcotmcr PITTSBURGH, PENNsYLvANxA.

' mimo-'ELECTRIC AMMETEB To-all whom it may concern:

Be it known that I, PAUL M. LINCOL, citizen of the United State residing at Pittsburgh, inthe State of provements in ThermofElectric A mmeters, of which the following is a specification.

My `invention relates to electri'c current measuring instruments, and its primary object is to provide a simple, accurate, and dependable ammeter, operated by means of a thermo-battery.`

I. show' one `embodiment of the invention inthe-accompanying drawing, wherein Figure l is anelevation, and Fig. 2 is a vertical cross-section.

Thermo-electric batteries have been employed for measuring currents, but they have not been efficient because there has not been provision for radiating the heat from the cold joints, and lthe thermo-elements have not been properly pro ortioned, and for other reasons. Brieiiy Femploy a resistance element carrying and heated by the whole or `a part of the current to be measured and employ this heat to excite a thermo-batt'ery, and thereupon measure the difference of potential between the terminals of the thermo-battery by means of a voltmeter, which thus indicates the temperature elevationand consequently the 'amount of current causing it.

As shown in the accompanying drawing,

I attach the leads L' and M. carrying the vided with radiatingr wings E, E.

current to bejneasured to the two ends of a resistance element .A, of material such as iron, manganin, nichrome, ctc., which is preferably of U-shape and envelops the hot joints of the elements B, C. The opposite endsof the elements B, C are embraced by any convenient form of radiator D which is proi I may employ any other form of meansto make the radiating surfacc'of the hot ends small compared to the radiating surface of the cold ends. Preferably the radiating wings E, E, are made of copper, and the gripping loops both at l) and A may be in sulatcd from the thermo-elements by mica, or other heat resisting insulator as shown at-G andH.

The thermo-elements should be in considerable number in order to insure 'accuracy specineana nf Letters raient.

y iennsylvania, have invented certain new and useful Imcase the copper bars B are thinner than the thermo-battery comprising the Patented June'15,.1915.

Application fied Yebruaryl, 191B. Serial No. 748,035`

' and positiveness inaction; and 'preferably make them of cor per :and constantin, for example, and adjust the cross-sections of the respective elements in inverse tion toftheir thermal conductivity. n this Constantin. By' this means I secure two adroporvantages; the heat conductivity is uniform forvall-the elements, and as electric conduc-v tiyity is proportional to thermal conductivity, the-condition` of the electric circuits are best. 7

The terminals of the thermo-battery are connectedby leads N and O, as shown, to any convenient form of voltmeter, V, and I prefer .to construct this latter instrument of the same material o1' material having the v same temperature co-eficient'as theheating or resistance member A', so that the'e'ntirveQ` apparatus is independent of the tem Aerature of the surroundm atmosphere.,lr as the'resistance o the voltmeter windings changes with ,change of temperature, the resistance of the e1eme'n't`A will change in like direction and prorEo'rtionf-having the same temperature `co-et cient. Therefore asthe resistance of the voltmeter increases thereby hat is,

demanding a higher voltage to cause a'given indication, the heat lost iu the heating ele:

ment also increases,thereby causing a higher temperature difference between the hot and cold .joints of the thermo battery in the same ratio.

l 0f course, on account of the 'time required to' change the temperature of the element .A in operation, there will be a ,lag in the indication. This -time lag 'I may adjust by theJ mass` of material "in the element A. A con venicnt way to do this is to surround the element A with a mass of 'metal J to actas a heat' reservoiigiagdkit is of, course electricallyinsulated, as bysti'i'p of mica. I. Also in order to prevent escape ofheat otherwise than, along the bars B and C, I preferably surround the heat reservoir J with a covering 'of asbestos K. This control over the sluggishness of the'instrument is of especial value where it is used to lndicatea maximum-demand, because we may thereb adjust the length of time for the heated mints to attain thc final temperature correspondingr to a given average current. The volt! meter V, in addition lto its regularA pointer 1, has an additional pointer P which is illustrated its iise,l what I claim is l, f 11. electric current'v meter [comprising anfeiexnent heated bythe current tobe measi11;ed,'"a heat absorber a' radiator connectedthereto,- a thermcouple with terminals' thrmaicontfict res eetively with" said heat?,

element andra iator, andl an indicator A of voltagejin circuit A Withsaid Ithermocouple.

2. An ammeter 4compri-sing a hetingconductor,;a1a'rge heatg reservoir surrounding pushed aroundby IP, but ,isl supplied with-a gp'awl Rfb which it is 'retained at itsy maximumrea ing bythevratche't Q.

,:iHaiffng thus described my invention andv subscribed mynaine in the 3Q IIA-1an ammeter, the combination with a l vqltme'ter, of a thermo 'couple .of a. heatin A elemeiitfor exciting said thermoeougle, an

a heatA .reservoir s urro'undin Asaidl e1ement,` and insulated there rom;

4. The combination with a thermoelectric generator operated by heat produced by eating a current'uto .be measured, 'of -aheat ab" sorber thereon adapted to suppress effect of temporary variations' of current2 and a c011- .necte'd vo1tmeter having a device to "indi -eatev the` maximum reading ofthe thermo battery, Substantially as described.

Invv testi 'ony whereof I have hereunto presence of the vtwo subscribed' Witnesses.

' PAUL M LINooLN.A

Witnesse'm 1 Jo. BAiLY BROWN,

-FBEDK-STARB- 

